Core and coil arrangement



June 19, 1956 J. c. MARSH 2,751,564

CORE AND COIL ARRANGEMENT Filed May 9. 1952 t l r 9 JNVENTOR. 9 0 g JAMES c. MARSH A Horney United States Patent CORE AND COIL ARRANGEMENT James C. Marsh, Indianapolis, Ind.,-assignor'to Ransburg iElectro-Coating Corp., Indianapolis, Ind., a corporation of Indiana Application May'9, 1952, Serial No. 286,927 5 Claims. (Cl. 336-197) This invention relates to improvements, both as to apparatus and method, in the construction of electrical apparatus and in particular the invention 'has to do with improvements in rigidly positioning electrical coils about a core.

At the present time inductances of large size, particularly voltage transformers which convert commercial voltages to voltages of several kilovolts and higher, are in wide use. Many of these inductances have cores with outer dimensions of six inches and much more and utilize electrical coils weighing well over apound each. 'In the case of high voltage transformers, it is frequently desirable to immerse the entire transformer in oil in order to provide effective insulation and at the same time 'it is often desirable that the transformers be portable and to these ends transformer construction must be rigid and able to withstand considerable shock and movement.

Various methods-have been employed in order to locate or position the coils about the metal core of an inductance in such a way that the parts remain in fixed spacial relation to each other and at the same time the coils are prevented from rotating or moving around the core or slipping along the length of the core. In an attempt to prevent such movement a sheath or covering of some rigid material has sometimes been placed around the core and the coils slipped over the sheath. In such an arrangement where sheath was cylindrical in form, the sheath itself often tended to rotate about the core or to shift along its axis. At the same time numerous devices were employed 'in an attempt to fix the position of the ring-shaped'coils. Wooden wedges were driven betweenthe outside surface of the cylinder covering the core and the interior-surface of the coils, but these wedges had a tendency to slip and, more important, they tended to injure or break the coating and/or wire windings of the coils directly above or below the wedges. Another method was to put blocks of insulating material between the edges of the coils and the sides .ofthe core and then wrap the blocks in place by fabric tapes. However, again the blocks had a tendency to slip or creep and also there would;be undesirable fluctuations in the performance of the transformer due to the different dielectric properties of the wood, Lucite, fabric, or other materials used in such anoperation.

According to my invention the foregoing disadvantages are overcome by maintaining the coils in a fixed position aroundthe core by'the'use of two or more washers which are spaced along and supported on the-core. The heavier the coils and the greater the length of that part of the core over which the coils are to lit, the greater is the number of washers required. A hollow member whose outer surface is shaped to conform to the inner edge of the hollow coils and constructed of some rigid material, such as hard rubber or Lucite, is supported around the core on the washers. This cylinder has a groove or recess in its outer surface positioned between each pair of adjacent coils. The coils are locked in fixed position to the hollow member by a plurality of retaining members 2,751,564 Patented June 19, 1956 which are made to fittightly against the sides or faces of each coil, so that no relative movement between the core and the coils can take place.

The detailed manner of accomplishing the foregoing will be fully understood from the following detailed description, with reference to the accompanying drawings wherein:

Fig. 1 is a front elevation, partially broken away, showing'the construction of 'one embodiment of my invention;

tained within angle iron brackets 15 and 16 which are bolted together by bolts 17 and 18 and 19 and 20 respectively.

In assembly of this exemplary embodiment of my in vention, before upright segment 13 of the core is put into place and locked within bracket 16, the primary and secondary coils are positioned about upper horizontal segment 11 of the core. First, washer 21, whose interior dimensions are suflicient to just permit the washer .to he slipped over segment 1'1 of the core, is placed over segment .ll-and positioned against the sides of segment 14. 'Washer 21 is made of some suitable rigid nonconducting material, such as 'hard rubber, fibre or the like and is inthe shape of a hollow square with its exteriorcorners rounded. Next, primary cylinder 22, being a thin-walled hollow cylinder of some non-conducting material such as fibre or Lucite, is slipped over upper segment 11 and against the inner face of washer 21. Primary coil 23 is then wound onto hollow cylinder 22 and its lead-in wires 24 and 25 connected to plate 26 as shown. Inner cylinder 27, also made of suitable nonconducting material, is then slipped over the primary coil 23 and is positioned against washer 21. Washer 28, being identical in size and construction to washer 21, is then slipped oversegment l1 and positioned with its inner face against the open ends of cylinders 22 and 27.

Outer cylinder 30 -is next slipped over inner cylinder '27 with its opposite ends resting on the rounded exterior ends there is an annular or ring-like groove or recess 31 which in this embodiment is approximately in depth as more clearly shown-at Fig. 4, to which figure reference has been made. Two secondary coils 32 and 33 are slipped over the outside of cylinder 30 so that their two adjacent inner faces lie immediately over the outer edges of recess 31 which is the predetermined position for these two coils.

Two pieces of plastic or other pliable and non-conducting tubing is used to form outer retaining rings 34 and 35, of such circumference that they will snugly encircle the outer diameter of cylinder 30. These rings 34 and 35 are arranged in position to rest against the outer faces of coils 32 and 33 respectively. Suitable tape 36 of some strong but pliable non-conducting material, such as standard cotton tape or webbing, is then looped around outer retaining rings 34 and 35 and between coils 32 and 33 and cylinder 30 longitudinally to the axis of core segment 11. While temporary spacing blocks between the inner faces of coils 32 and 33 keep these coils in fixed such as fibre or plastic of such dimensions so as to fit over fabric 36 and into groove 31 is wound around the outer edge of cylinder 30 and over fabric 36 between coils 32 and 33 to form an inner retaining ring 37. This inner retaining ring or belt is then held firmly in place by wrapping it with several layers of suitable cotton tape 38 wound around and over ring 37 between coils 32 and 33. This cotton tape 38 may be secured in position by suitable adhesive such as Glyptal. The entier' coil supporting structure encircling core segment 11 is now locked into position by putting upright core segment 13 into place and securing it with bracket 16 which is bolted into place by bolts 19 and 20 as shown in Fig. 1.

It is noted that washers 21 and 28 are generally square and thus free circulation can be efiected of the oil in which the entire apparatus is immersed. However, different shapes of washers can be used, as for example a discshaped washer with a number of holes therein to permit free circulation of the immersing oil.

It is apparent that the foregoing apparatus and method will securely lock coils 32 and 33 into fixed position in relation to core segment 11. The pressure on both faces of each of the coils exerted by tape-wrapped retaining rings 34, 35 and 37 will prevent the coils from any tendency to rotate about cylinder 30. Tape 36 which interconnects rings 34 and 35 will serve to prevent the coils from shifting longitudinally along cylinder in either direction. Also, the pressure of rings 34, and 37 against the faces of coils 32 and 33 will be evenly distributed around the interior edges of each of the coils without tendency to break or injure the protective coating or the windings of the coils, but the small size of the retaining rings and fabric wrapping will be insuflicient to eifect the electrical performance of the transformer.

While an embodiment of my invention has been described wherein only two coils are locked into position, the invention may utilized to position three or more coils spaced along a core segment. Where more than two coils are involved, an annular recess will be required between each pair of adjacent coils so that there will be one less annular recess than the total number of coils to be positioned. Two outer retaining rings, such as rings 34 and 35 as described above, will be employed and all of the retaining rings will be joined together by suitable tape as previously described. Although there has been shown and described only one exemplary embodiment of my invention, the scope thereof is not intended to be limited by such detailed description but rather the scope of the invention is limited only by the following claims.

I claim:

1. In an inductance a core; a plurality of insulating washers spaced along and supported on the core; a hollow cylinder of insulating material around the core supported on the washers, which cylinder has an annular recess in its outer surface; two ring-like coils surrounding the core structure and positioned at each edge of said annular recess; two outer retaining rings of insulating material each fitted snugly against said cylinder and at least a portion of an outer surface of each coil; an inner retaining ring of insulating material fitted into said annular recess with its sides fitted snugly against at least a portion of the opposing inner faces of each coil and means for bending said retaining rings together.

2. In an inductance a horizontal core segment; a plurality of insulating washers spaced along said core segment; a hollow cylinder of insulating material supported on said washers and having an annular groove in the outer surface of said cylinder; two coils surrounding the cylinder and positioned on either side of said annular groove; two outer retaining rings of insulating material each fitted snugly against said cylinder and at least a portion of an outer face of each coil; an inner retaining ring of insulating material fitted into said annular groove and against at least a portion of the opposing inner faces of each coil; and means for binding said retaining rings together.

3. In a voltage transformer having a core and a plurality of coils having oppositely facing inner and outer faces and surrounding said core, apparatus for maintaining the coils in a fixed position around the core comprising: a plurality of insulating washers spaced along and supported on the core; a hollow cylinder of insulating material supported around the core by said washers, which cylinder supports the coils and has an annular recess in its outer surface between each pair of adjacent coils; two outer retaining rings of insulating material each fitted snugly against the outer face of each of the two outermost coils; a plurality of inner retaining rings of insulating material each fitted into one of the annular recesses in the cylinder with the sides of each ring fitting snugly against the sides of adjacent coils and means for binding said retaining rings together.

4. In electrical apparatus a cylindrical casing of insulating material surrounding a core, said casing having a peripheral recess in its outer surface; two hollow ringlike coils having opposed inner and outer faces, said coils being supported on the casing with their inner faces facing each other and substantially flush with the opposite sides of said annular recess; two outer retaining rings of insulating material each fitted snugly against the outer surface of said casing and an outer face of each coil; an inner casing-encircling retaining ring of insulating material fitted snugly into said recess and against the inner face of each coil; and means including a flexible webbing for securely binding said retaining rings together.

5. In electrical apparatus a core-surrounding casing of insulating material having a casing-encircling recess in its outer surface; two coils each having opposed inner and outer faces, said coils being spaced on said casing with their faces facing each other from opposite sides of said recess; two casing-encircling outer retaining members of insulating material each fitted snugly against said casing and an outer face of each coil; an inner casing-encircling retaining member of insulating material fitted snugly into said recess and with its sides fitted snugly against the inner faces of each coil; and means for binding said retaining members together.

References Cited in the file of this patent UNITED STATES PATENTS 1,208,577 Kraemer Dec. 12, 1916 2,459,374 Goodrich Ian. 18, 1949 FOREIGN PATENTS 105,978 Germany Oct. 28, 1899 258,046 Great Britain Sept. 16, 1926 

